It is conventional to provide, by using a navigation apparatus for navigating a travel route to a travel destination, weather information about the travel destination or the navigation route. The navigation apparatus displays acquired weather information together with a map to attract attention of a vehicle user to weather condition.
According to a system disclosed in JP 2006-84250A, for example, a display device for displaying road map displays interrupt information including an expected course of a typhoon, when a travel destination or a present position is included within an area of influence of the typhoon. Thus, the system attracts attention of vehicle users to weather information about a travel direction and the like.
This system, however, fails to take into consideration characteristics of a vehicle and a travel road. For example, even if bad weather in a travel direction is warned in the course of traveling a road such as an expressway, which has few branch roads, it is often not possible any more to avoid the bad weather near a destination or a navigation route after passing a branch point. Some vehicles are fully equipped to be able to travel under bad weather. The warning of bad weather therefore occasionally causes unnecessary detour or rest, which will prolong travel time to the destination.